in a nutshell, yes: you're right not to go into too much detail with these background characters, though you can go into superficial detail. for example, you could describe their tattered clothing, or if they're some strange species, you could describe the series of ridges on their forehead and their unusual yellow eyes. background characters are there primarily to populate the world of your story. since we're on the subject, let's take a look at the different levels of characters and what they do.
1 ) PRIMARY CHARACTERS
primary characters are often referred to as "main characters" or "major characters." they are the characters with major roles in the story, either because the story revolves around them, their actions help to move the story forward, or they play an essential role in supporting the protagonist.
Protagonist - the protagonist is the main character of the story. their actions in pursuit of a goal is the primary force that drives the story forward.
Antagonist - the antagonist isn't always a primary character, but if they are a fleshed out living being with their own conflict and goals that drive their opposition of the protagonist, they can usually be considered a main character.
Deuteragonist - the deuteragonist is a second protagonist whose goal pursuit/actions drive the story as much as that of the protagonist. tv tropes offers the following examples of protagonists with deuteragonists: jon snow/daenerys targaryen, lorelai/rory gilmore, anna/elsa, sam/dean winchester. you can also have a tritagonist, and some would argue going further, though the more main characters you have, the less likely it is that the story revolves around them equally compared to the protagonist, deuteragonist, etc.
Supporting Characters - these characters support your protagonist, helping to tell their story. they often have their own goals, conflicts, and arc, which can be important to the story but shouldn't be the focus of the story. they don't play a major role in moving the story forward, but they can influence the actions of your protagonist (and deuteragonist/tritagonist if you have them) and do help the reader to understand them a little better. best friends, sidekicks, mentors, parents/siblings, and love interests are the most common supporting characters.
2 ) SECONDARY CHARACTERS
secondary characters are often referred to as "minor characters." they are the recurring characters who populate your main characters' lives and help to inform the reader (and sometimes the main characters) about circumstances of the story and the story's world. although they may be lightly fleshed out, they do not have their own goals/conflicts/arc and have only a superficial effect on the main characters' actions, if any at all. Secondary characters should at least have a name and basic description.
in a story set at a school, for example, students and teachers important enough to be named, but who don't have a pivotal role in the story, would qualify. in twilight, rene, esme, emmett, jasper, the clearwater's, and sam would all qualify as secondary characters. in harry potter, the weasley's (except for ron, of course), the dursley's, cho chang, harry's parents, and filch would qualify as secondary characters.
3 ) TERTIARY CHARACTERS
tertiary characters, often called "background characters," are really the "extras" of your story, primarily there to make your story's world function realistically. after all, if your character goes to a restaurant, someone has to take their order, and they can't walk into a crowded party without party goers.
i like to divide tertiary characters into two types: functional and flat.
functional tertiary characters are like extras with speaking roles. They do serve a purpose, albeit a limited one. they may be the hotel clerk who checks your protagonist into their fancy resort, or they may be the nameless but kind-hearted guard your imprisoned protagonist prevails upon for an extra loaf of bread, who is then conked on the head as your protagonist takes the opportunity to make their escape. these characters can be named and lightly described, or they may be referred to in basic terms like, "the blonde hotel clerk" or "the kind-hearted guard." so, the server who takes your character's order at a restaurant would be a functional tertiary character.
flat tertiary characters are literally just background characters. they're not named, they're not described beyond the very basic necessary details. these are the random party goers in your crowded party scene. they're they well-dressed shoppers bustling through the department store at christmas. they're the colorfully dressed citizens of panem.