Please explain these audiogram acronyms

My audiogram contains a table with the label SRT. It contains results for Left and Right HL, MCL, and UCL.

Please explain what these bold text acronyms mean.

Speech Reception Threshold - This is where you could discriminate the easy 2 syllable words the audie was saying

Most Confortable Level - This was the volume you said was a comfortable listening level. The audie then started rattling off one syllable words that are not so easy to discriminate.

Upper Comfort Level - This is where you said, that is too loud for me, please stop!

Hearing Level - This is the lowest level where you could hear the beep