As you want to get the details of differences between UPSC and IAS so here is the information of the same for you:

IAS is basically a service rendered in the administrative side for the Government of the country.

UPSC is the body which conducts the entrance exam for this purpose.

There are several other entrance exams like IES, IFS conducted by UPSC for various positions at the Central Government level.

So if you wish to become an IAS officer you need to check for the details of recruitment in the UPSC site.