It's easier to understand the simple endings without 것이다 first. - (present) 사랑하여요/사랑해요 (하여요 is not used much). - (past) 사랑했어요/사랑하였어요. - (future) 사랑할 것이에요/거예요. (it can also mean an intention sometimes). - (intention) 사랑하겠어요. (like "I will/would"). -ㄹ/ㄴ/는 것이에요/거예요 makes an indirect form with a deferred sense, a bit similar to "it is that (...)". -ㄹ 거예요 is kind of special, as it creates future tense (-ㄹ/을 expresses what's to come or expected). -는 거예요 creates a present tense indirect sentence, similar in meaning to the simple version but more indirect and with a nuance of observing the situation. Similarly, -(으)ㄴ 거예요 creates a past tense version. - 집에 가는 거예요 = I'm going home. - 늦게 일어난 거예요 = (It is because) I/they got up late. To summarize, - 사랑해요 - (present tense) direct and plain meaning. - 사랑하는 거예요 - (present tense) similar meaning, but indirect and nuanced like an observation. - 사랑했어요 - (past tense) direct and plain. - 사랑한 거예요 - (past tense) observation nuance. - 사랑할 거예요 - (future tense or expressing an intention - no matching simple sentence form) 것 in 것이에요 (which is shortened to 거예요) just means a fact in these sentences, so -ㄹ/ㄴ/는 것이에요/거예요 is a bit like "it is that (...)". It can create different connotations and nuances depending on the usage context, for which there seems no simple English phrase doing the same.