To add to ReverendDexter's great description of Toyota codes:
U as part of the detail code is for Japanese emissions compliance.
L is for transverse mounting but hasn't been used since the era when they had a lot of the same engines in both orientations....in other words it only applies to the mid-late eighties stuff.
S as part of the detail code is used for direction injection, and is always coupled with an E for EFI.
The big mistake people make with Toyota engine codes (and a source of most of the frustration) is that they don't contain displacement info. Sorry, that's just the way it is and you have to look it up. The VIN plate says, Google is another good source if you don't have the car in front of you.
The cool part is that Toyota chassis codes contain engine family, so you know that an RA28 Celica is a 2nd-generation Celica powered by an R-series engine, and an MA70 Supra is powered by an M-series engine. A JZA70 Supra must be from overseas because it is a 7th-generation car, but with the JZ-family engine, which we didn't get here until the next body style.