Intuitively explaining the difference between a combination and permutation I'm having a hard time trying to determine when to use combination and when to use permutation with a problem.  Can someone offer a clear and concise explanation or general rules to follow so I don't get tripped up on similar problems?

For example: How many ways are there to select five players from a 10-member tennis team.

My approach would be that there are 10 ways to choose the first spot, 9 for the second, 8 for the third... so the total is 10!/5!; but apparently this is a combination problem.

I'm just having a hard time telling the difference between the two.  Are there any questions I can ask myself before I begin to really solidify what the problem is asking for?

Thank you!

EDIT:

Here's another problem I'm confused with:

Suppose that there are 9 faculty members in the mathematics department and 11 in the computer science department. How many ways are there to select a committee to develop a discrete mathematics course at a school if the committee is to consist of three faculty members from the mathematics department and four from the computer science department?

Why is the answer 9!/(3!6!) * 11!/(4!7!) rather than 9!/(3!6!) + 11!/(4!7!)?
Regular rule, Permutation is when order matters. You can memorize it with P ermutation-P osition. Combination on the other hand doesn't care in which order the elements are chosen. 

As in your first example, you want to choose $5$ players, but no other information is given so you assume order isn't important.

Note that I the problem stated $5$ player to form a hockey team, then order could have mattered, for say center, Left and right wing, and left and right D player.

For your second example, note that for each subcomitee of $3$ members of math, there are $11!/(4!7!)$ subcomitee of members of CS so you have to multiply them
It is a matter of translation: In your problem if you have a collection (without order) then you asking how many sets can you form (combination). If you have an ordered collection (or chain, ranking, etc.) then you are asking about how many ordered sets you can form (permutation).