The word "start" has several meanings, depending on its context.
1) Beginning or commencement: This is the most common usage of the word - to indicate that something is just beginning or has just started happening. For example, "I'm excited for my new job to start!" or "The race began with a loud start."
2) To initiate or activate: The term can also be used in the sense of starting up an engine, machine, program, etc., by turning it on, pressing a button, or otherwise activating it. For example, "I started my car this morning" or "Let's start the computer."
3) To begin to engage in something: This usage implies that one has not been doing something before but is now starting to do so. An example would be "She decided to start exercising regularly."
4) A point of origin or departure: In this sense, "start" refers to the beginning place or point from which an action, journey, etc., begins. For instance, "The bus stop was just around the corner from my house, so I could easily start walking there."