When history says "Alexander founded a new city," what is being described here?

by [deleted]

For example, did he literally choose the location for a brand-new settlement? Or did he just take an existing settlement and decided to make it more important by leaving a bunch of soldiers/officials there? In either case, how many people did he leave behind? Did this affect the fighting capabilities of his army? Did the Greek settlers outnumber the locals, or vice versa?

Thank you for any responses

Searocksandtrees