If you mean Spanish spoken in Spain versus Spanish spoken in Latin America, then it's basically the same difference as English spoken in England and the US. Some vocabulary words are different, the accents are different, slang is different, etc. etc. Of course there are also regional varieties in the Spanish spoken in Spain (just as there are regional differences in the English spoken in the UK). The main grammatical difference between Spanish Spanish and LA Spanish is that in Spain they use the plural you form 'vosotros' (together with its own special verb endings) as well as 'Ustedes', but you don't have to learn these in LA Spanish as they use only the form 'Ustedes' which has much easier and more logical verb endings.
Lived in Spain for a while and now speak Spanish with Latin Americans.