What is BW on HANA BW on Hana

Dear Experts,

Can you explain me the below. i have a lot of confusion in between 😔😕

1. What is BW on HANA BW on Hana.

2. Can we replace ECC data base with HANA(instead of traditional database, can we use only HANA data base?)

3. Standalone HANA

4. HANA side CAR

Thanks a lot in advance