'Which' vs 'That'

[scruffy]

I'm trying to polish up on my grammar and am wondering when it is appropriate to use 'which' over 'that' in introducing relative clauses.

For example:

"I often buy cheese that is imported from Paris."
"I often buy cheese which is imported from Paris."

or

"He showed us how to create a computer game which was very interesting."
"He showed us how to create a computer game that was very interesting."

I attempted to search the forums but I'm afraid I don't know the English terminology enough to get past the 'simple word' filter. I couldn't find a way to phrase a question [which?/that?] would register.

[Alan]

Both are possible, but in restrictive relative clauses such as these 'that' is more common/natural.