A character's background describes the sort of life they lived before they began adventuring. Every background gives a small list of features, typically 2 to 3 Skill Proficiencies, 0 to 2 Languages, and 0 to 2 Tool Proficiencies. In addition to this, each background gives a +1 to one of your Ability Scores from a list appropriate for the background, and each gives a primarily roleplay-oriented feature. In general, a background is designed to be only minorly impactful to a character, as to make it non-detrimental to choose based on character backstory over mechanical priorities.
Each of the backgrounds below are sorted by their source, and they include a short description of the background to make choosing easy.