5 Acrynom for IFR

MEA  - Minimum Enroute Altitude 

lowest altitude along the route that assures navigational signal coverage and obsticle clearance

MRA  - Minimum Reception Altitude 

lowest altitude to recieve navigational coverage

MCA - Minimum Crossing Altitude 

Lowest altitude a fix can be crossed and continued on allowing to clear obsticles in normal climb

MOCA - Minimum OBstruction Clearance Altitude 

Lowest altitude to clear obstacles and recieve VOR coverages within 22nm of a VOR

MAA - Maximum Altitude Altitude 

Maximum usable altitude for airspace structure

holding-

Holding 

• What Radial are you holding?
• Righ hand (Standard) or left hand hold
• Time/Distance hold? 
• Draw the Hold on a VOR
• Where are you in relation to the VOR?
• What kind of Entry are you going to make Direct/Parallel/TearDrop?

Note:

ATC in concern about the Inbound leg of the Hold, the length of it (distance or time) and to be on the  protective side

They do not care how you enter the hold