my car will turn over,but want start,what could it be? on 2002 Saturn LW300

I have a tank full of gas,I'm lost.

an engine must have the basics: fuel, fire (ignition) and
compression. if you are capable and have some diagnostic ability, you can start with the basics. is there spark when cranking? is there correct fuel pressure and volume?
if these basic tests scare you, it is best to have someone
else diagnose this problem.
2 more answers , 1 more comment
take out the spark plugs, spray carb cleaner on them, let them dry, and put them back in.
no fuel pressure or no spark broken timing belt