LJ
an Initial Approach fix (IAF) is the fix of an instrument approach at which the aircraft leaves the en route phase of operations to commence the approach...so falls off the STAR onto the approach plate
an Intermediate Approach Fix (IF)is the fix at which an aircraft enters the intermediate approach segment. THAT is either the segment between the IF and the Final Approach Fix, or (more usefully) between the end of a reversal, racetrack, or dead-reckoning track and the Final Approach Fix....basically when you're lined up on the final approach track.
The Final Approach Fix (FAF) is segment of an instrument approach in which alignment and descent for landing are accomplished...i.e. when the final approach track intercepts the (nominal) glidepath.
as to the circles, do you mean the three rings made up of dots, in which case it's an NDB (CHT is an NDB) or a circle with a + in it which is a Visual Reporting Point (VRP)
BNN EPM LAM OCK would be IAF's as the STARs finish there and the approach plates start there. Spookily, the EGLL AIP entry AD2 EGLL 7-7 entitles the plate "Initial Approach Procedures".
Who says the system doesn't work?
Tori