Any grammar that can be parsed by an LR(0) parser can be parsed by an SLR(1) parser. However, SLR(1) parsers can parse a larger number of grammars than LR(0), and so on.
Makes sense? the power represents here the ability to accept grammars.
At syntax analyses phase we use parsers and therefore categories them as LL(0) SLR(1) and so on
And for a grammar - the languages they are able to recognize. We categories as CFG CSG and so on.