The main players in this week's parsha are popularly referred to in Hebrew as the מרגלים (m'raglim), generally translated as spies. Interestingly, that word does not appear at all in this story. It does figure in the story told in the second chapter of Yehoshua, but we'll come back to that in a bit.
The command here is:
במדבר פרק יג (ב) שְׁלַח לְךָ אֲנָשִׁים וְיָתֻרוּ אֶת אֶרֶץ כְּנַעַן אֲשֶׁר אֲנִי נֹתֵן לִבְנֵי יִשְׂרָאֵל אִישׁ אֶחָד אִישׁ אֶחָד לְמַטֵּה אֲבֹתָיו תִּשְׁלָחוּ כֹּל נָשִׂיא בָהֶם:
Bamidbar Chapter 13 (2) Send men for you, that they will explore the land of Canaan that I am giving to the Children of Israel; One man, one man for (each) tribe of his fathers shall you send, every prince thereof.
The key word here is ויתרו (v'yaturu) which derives from the root לתור. The meaning of this word is not absolutely clear but it seems to involve the idea of wandering and exploration. Significantly, the same root word appears at the end of this week's parsha:
במדבר פרק טו (לט) וְהָיָה לָכֶם לְצִיצִת וּרְאִיתֶם אֹתוֹ וּזְכַרְתֶּם אֶת כָּל מִצְוֹת יְקֹוָק וַעֲשִׂיתֶם אֹתָם וְלֹא תָתֻרוּ אַחֲרֵי לְבַבְכֶם וְאַחֲרֵי עֵינֵיכֶם אֲשֶׁר אַתֶּם זֹנִים אַחֲרֵיהֶם:
Bamidbar Chapter 15: (39) and they will be for you as fringes and you will see them and you will remember all of the commandments of God and you will do them and you will not wander after your hearts and after your eyes which you stray after.
Again, the meaning here is not absolute, but it implies in this context a kind of loose wandering.
We can contrast that with the story told in the second chapter of Yehoshua where Yehoshua sends two men (again the same word in Hebrew אנשים, as we see in the beginning of our story) but they are sent as מרגלים—spies.
יהושע פרק ב פסוק א וַיִּשְׁלַח יְהוֹשֻׁעַ בִּן נוּן מִן הַשִּׁטִּים שְׁנַיִם אֲנָשִׁים מְרַגְּלִים חֶרֶשׁ לֵאמֹר לְכוּ רְאוּ אֶת הָאָרֶץ וְאֶת יְרִיחוֹ וַיֵּלְכוּ וַיָּבֹאוּ בֵּית אִשָּׁה זוֹנָה וּשְׁמָהּ רָחָב וַיִּשְׁכְּבוּ שָׁמָּה:
Yehoshua Chapter 2 (1) And Yehoshua the son of Nun sent from Shittim two men, spies, secretly saying: Go and see the land and Yericho. And they went and came to the house of a woman, a prostitute and her name was Rachav and they slept there.
The contrast between the two stories and their outcomes is enormous. In short, though, Moshe's contingent was comprised of 'men' which we have seen elsewhere is a description of men of standing and importance, in this case they were the princes/leaders of each of the tribes. However, the command that they 'explore' or 'wander' seems to have been taken by them as a kind of blank check—that is they were supposed to be looking for certain general indicators, as are specified by Moshe later, but otherwise were sort of on their own to 'look around.'
Apparently Moshe thought it prudent and politically correct to send the prince from each tribe in a public sort of way. He must have thought that by using such transparent means to gather information it would be clear that he, Moshe, wasn't hiding anything from the people. He also assumed, naively, that they would come back with positive, or at least neutral, reportage.
Alas, Moshe's faith in that regard was misplaced. While they did bring back correct information, the way it was reported along with their own commentary on what they saw turned out to be extremely negative. The people, whom we know to be wary of Moshe and of God from other stories, are quick to seize upon the negative report. It is almost as if they knew in advance that things would be bad for them in the Promised Land and needed very little encouragement to believe such stuff.
Chazal learn a great deal about Lashon Hara from this parsha. Lashon Hara (literally 'evil tongue', refers to gossip of sorts or speaking ill of someone or something) is by definition 'true' (there is another term for speaking ill in false terms). However, by its nature it is a limited truth as Lashon Hara inevitably leaves out information which does not suit the teller's version of events. If you read our parsha carefully and understand what Calev is saying to the people, you will see this is true here, as well.
Yehoshua was much more careful in his use of 'men.' He sent spies, apparently professionals and not political appointees. He sent them secretly, which implies that even the Children of Israel didn't know about their mission. They were sent to gather specific intelligence and not to give some general report. And they reported directly to Yehoshua and not to the people at large.
The difference between לתור (to wander/explore) and לרגל (to spy) are very sharp and evident.
Likewise, the tendency to see what we want to see, to believe what we want to believe and to ignore truth are dramatically displayed in this parsha.