~하다 is basic verb, 하 is original verb, 다 is ending word. 하 + ㄴ (present) + 다 = present So, 사랑한다 means 'I love you (now)' 해 is ending word So, 사랑해 is just 'I love you' Usually, Most Korean doesn't care about this. It's all about the nuance

사랑한다 is basic form and 사랑해 is more causal form you can say 사랑해 to same ranker like you(your friends or boyfrind) or lower ranker(your younger brothers and sisters or kids) meanig is same but just form is differenent

Thank you, i was wondering too. Stay kind and stay safe.