Generically, tag along trailers are typically smaller camper or utility trailers that are hitched to smaller cars and often motorcycles with a simple ball hitch. They usually don't require brakes or any sort of load leveling or anti-sway hitch. The term is not derogatory in any way that I'm aware of. Harbor Freight as I recall, uses the "Tag-Along" brand name on some of their small trailers.
A typical tag along trailer that could be towed by either a small car or a motorcycle:
Dutch
2001 GBM Landau 34' Class A
F53 chassis, Triton V10, TST TPMS
Bigfoot Automatic Leveling System
2011 Toyota RAV4 4WD/Remco pump
ReadyBrute Elite tow bar/Blue Ox baseplate