A big source of confusion here is that "Economy Light" is not the marketing name of a United product. It's unclear what product or status the OP is referring to, so I made a quick chart to illustrate the differences.
Within the US, United will market
Basic Economy fares. These
always have a booking code of N -- you have a Basic Economy ticket if and only if you have a booking code of N. This is the most restrictive type of fare United sells.
In European TATL markets, United sells a fare listed as
Economy (first bag charge/no changes allowed). Because this is a mouthful to say, and because it aligns with the same offering from European carriers, this is usually called "Economy Light" here on FT. These fares use normal Economy booking codes, but the last three letters of the fare basis are
LGT.
The chart shows some of the allowances, depending on whether you are a United Premier Gold, or Star Alliance Gold through a different airline's FFP.
Code:
Basic Economy (N) -LGT Fares (normal rbd)
Benefit (domestic only) (European TATL markets)
UA Gold OAL *G UA Gold OAL *G
================================================================
3x70 (UA)
Baggage Allowance 2x70 1x50 1x50 (OAL) 1x50
Full-sized carryon Yes Yes Yes Yes
Group 1 boarding Yes Yes Yes Yes
Economy Plus No No Yes No
E- Seat Selection $$ $$ Yes Yes
Upgrades No No No No
Changes (incl. SDC) No No No No
Lounge Access No [1] Yes Yes Yes
MP Premier Credit No No Yes Yes
[1] No access for UA*G on a domestic itinerary in any cabin