They are "day laborers." People who hang around there hoping to find work helping with your home repairs, painting, appliance installation, landscaping, or other projects etc.
Lots of illegal immigrants desperate for work
Then you'd need to prove your identity and pay taxes on what you earn. This is for illegal immigrants working under the table.
I go to Home Depot more than is reasonable, and I’ve never been approached by them. You typically would need to solicit them yourself. In general I find them to be respectful and pleasant - I imagine otherwise they would get customer complaints and Home Depot would have them trespassed immediately.
From others experiences I’ve talked to, they usually form “crews” with one main “crew chief” guy who speaks English you negotiate a rate and number of workers you need, and any specific skills like concrete, framing, etc. beyond simple labor. You generally are expected to provide any tools needed to complete the job beyond what fits in a standard tool belt.
You need to go to the home improvement store to get materials for your job anyway, you can also pick up some people to help, too.
Why fuss on an app trying to figure out who to hire, when you can head over, say 'hey, who knows how to dig a foundation' or 'who can help me hang a door' or whatever your job is. Maybe find the worker first and they can help you shop for the stuff you need.
Drive them back to the lot at the end of the job.
They go in to grab materials, leave with materials and some potentially new workers. If it works out (and it often does) they may use them for other projects, too.
Source: My father in law was a carpenter for about 40 years