The three kinds of option, honestly
Live chat modules. A chat box tied to your staff. Useful while someone is at a desk, silent otherwise. Cheap or free, and the right answer if you have people and want nothing automated.
Universal widgets. A script tag from a general chat vendor. Works on any site, but it sees your storefront the way a visitor does — it can read published text, not your product table, and it usually cannot look up an order at all.
Native modules. Installed in your back office, connected to your data. Products, categories, prices and policy pages sync, so answers are about your actual catalogue, and order-status questions can be answered live.
The PrestaShop Addons marketplace and the wider module ecosystem carry all three kinds, and the listing rarely makes clear which one you are buying. The checklist below is how to tell.