Ok so me and my friend here are confused out of our minds?

It can be a little confusing. Czechoslovakia used to consist of Czechia and Slovakia ( not to be confused with Slovenia ). On January 1, 1993 the country Czechoslovakia peacefully split into the Czech Republic and Slovakia. So , Czechs and Slovaks lived in Czechoslovakia before and now most Czechs live in Czech Republic and most Slovaks live in Slovakia. They are different nationalities living in peace next to each other.