Keyless-Go vs. Remote Keyless Entry & Engine Start




I am familiar with MB's Keyless-Go (leave the key in pocket, tap the door handle to unlock, get in, push the start button, go.)
I'm also familiar with a "Smart Key System" (push the unlock button on the key to unlock the doors, get in, insert and turn the key in the dash to start, go.)
But I am not familiar with the terms "Remote Keyless Entry" and "Remote Engine Start." Do I assume correctly that for these items, it is necessary to remove the key from one's pocket and have it in a hand to push buttons on the key.
So does "Remote Keyless Entry" mean the same as "push the unlock button on the key to unlock the doors as in the Smart Key System.
And wiith "Remote Engine Start" is it correct that one does NOT need to insert the key into the dash and turn to start the engine, but could start the engine while approaching the unlocked vehicle? If the key is not inserted in the dash, how is the engine shut off?
Thank you for your insights and help to clarify this terminology.






