Guests are people that you can communicate and collaborate with on Glip, but do not work at your company. They might be clients, partners, contractors or vendors. Anyone that you don’t consider an employee. Any time you add someone to Glip, you’ll be asked to specify whether the person is a co-worker or a guest. The one exception is when you add someone with an email address on your company’s private domain. For example, if Acme Co (acme.com) is on Glip, anyone with an @acme.com email address is automatically considered a co-worker.
Within a given conversation, guests don’t have many limitations. They can post anything (chats, tasks, files, etc.) and can see the entire conversation history. Importantly, though, they don’t see anything on Glip, be it people or teams, outside of the conversations that you’ve explicitly included them in. For example, say Dave from Acme adds Jill at ClientCo as a guest and then adds her to a “Launch Project” team that includes Peter and Tracy from Acme. Jill will only see the Launch Project team on the Teams page, and only Dave, Peter and Tracy on the People page. She won’t see any other Acme people or teams.
Note that Jill and other people from ClientCo can start to use Glip for their own purposes, without needing to create a separate account. You only ever need one account on Glip. (Learn more.)
Beyond what people and teams they see, guests do have some other limitations. Guests can’t add people to your company, can't create teams for your company, or generally manage your teams (e.g., add/remove people, rename, create folders, etc.).
If your company has a subscription to Glip's Standard plan there’s no reason to hesitate about adding as many guests as you need. You don’t have to pay for guests as part of your subscription.