Changes to your domain details are dependent on when ISPs update their records, some do this hourly, some daily, some less often. If you are pointing your domain to a new hosting service then you should allow about 72 hours for full propogation.
Changes to content take place as soon as they are uploaded BUT browsers are designed to save bandwidth and load faster by not going back across the web to re-read recently accessed files. With the major PC browsers you just need to press F5 to force a page to reload from scratch. For smart phones, tablets or Macs consult the vendor's documentation.