As you might have noticed already, there are two types of adjectives: the i-adjectives and the na-adjectives. There is not a meaning difference between them (why they are “i” or “na” type), there are simply different words, which are divided in two groups.
As the name indicates, i-adjectives end in “i”, and na-adjectives end in “na”. There is a little difference, which is when writing a sentence, the “i” in i-adjectives appears, but the “na” from na-adjectives doesn’t. For example:
1) 私の家は狭い (わたしのいえはせまい, watashi no ie wa semai) -> My house is small.
2) 私の家はきれい (わたしのいえはきれい, watashi no ie wa kirei) -> My house is pretty.
This was the present pattern.
In the past pattern, the “i” from i-adjectives gives place to “katta”, and in na-adjectives you only have to add “datta”. Examples below:
1) 私の家はせまかった (わたしのいえはせまかった, watashi no ie wa semakatta) -> My house was small.
2) 私の家はきれいだった (わたしのいえはきれいだった, watashi no ie wa kirei datta) -> My house was pretty.