Within is closer to inside - it mainly refers to something like a building where you are physically in (or inside). In can also mean a state or an organisation, so you can be "in trouble", or "in school" but not "within trouble". In’ and ‘within’ are both prepositions that refer to spatial or a logical relationship between two or more subjects in a sentence. ‘In’ is specifically defined as being inside while ‘within’ implies being inside of a given set of parameters relative to the object it’s linking to and not actually inside of it.