Broadly speaking, speedlights are the portable solution where we need to increase the light level and / or create our own lighting qualities. Most of us with more than a casual interest in photography own several. For a beginner, the most likely requirement is to help cope with low lighting indoors, usually shooting events or portraits. For these purposes look for a dedicated speedlight with a tilt, swivel, zoom head so the light quality can be improved by bouncing off a nearby surface. In this context "dedicated" means the unit communicates with your make of camera to achieve correct automatic exposure. This is useful, for example, when shooting people engaged in activities such that the conditions are rapidly changing.
I disagree with the recommendation by ac12 (sorry). These days most of us operate off-camera flash with wireless triggers, or more sophisticated controllers that can adjust multiple speedlights remotely. Many advanced speedlights even have these functions built-in. Simple triggers are very inexpensive and much more versatile than cables. I also wouldn't recommend a flash bracket unless you found a particular need for one. Long ago they were one of few options available to help improve results from on-camera flash, but the difference made by a flash bracket is minimal and there are countless other accessories to consider, such as collapsible softboxes and reflectors. In most situations the bounce head itself is going to be preferable to the modest difference made by mounting on a bracket.
Camera manufacturers' own speedlights offer very poor value for money. Yongnuo speedlights are indeed popular as they offer a lot of specification for a very low price. I don't own any of those but I have some from another well regarded budget brand, Neewer. My currently preferred speedlights are from Godox, whose products tend to be of superior construction and design for only a little more money than the cheapest brands. I strongly recommend the Godox TT685C, which pleased me so much the first time I used it I immediately bought another. If that isn't cheap enough let us know your budget, and ideally the kind of photos you plan to take, so we can make appropriate suggestions.