At a high level, startup accelerators and incubators are organizations that seek to help startups attain success. Startup accelerators tend to focus on providing startups with mentorship, advice, and resources to help the startups succeed, including a Demo Day, a day to focus the attention of the startup investor community on the startups through hosting a series of investments pitches from the startups to startup investors.
Accelerators tend to not offer dedicated office space to startups (and may encourage startups to find their own dedicated space), but may have a physical location for shared resources and accelerator events such as invited guest speaker talks and advising office hours. Incubators tend to offer dedicated office and development space to the startups for a set period of time.
Startup accelerators and incubators can get involved at all stages of a startup’s development, from idea stage to revenue-generating, late stage. However, most tend to focus on relatively early stage startups, as this is when companies can typically most benefit from outside help.
Startups are usually admitted in batches, with many incubators and accelerators offering 1-3 batches per year. Some focus on a specific industry, market, technology, stage, or other thesis, whereas others are more generalists. Most seek to run an application and screening process.
However, while a handful of accelerators and incubators have been very successful in helping startups attain success, being admitted to a startup accelerator or incubator is not a guarantee for success to a startup founder, and not a guarantee of a sound investment for a startup investment.