What is difference between update and upgrade?

An upgrade is the act of replacing your product with a newer, and often more superior, version or similar product. Therefore, an update modifies your current product while an upgrade totally replaces it.

Update is a no-cost update
upgrade is an update with a fee

I agreed with @Amit K.
Update means you are making some changes in your existing program or devices. Upgrade means you are purchasing any kind of existing services to get more feature.

Update mean minor change in existing software or web version to improve security and function or fixing bug.
Upgrade mean whole existing version change to new improved interface.

update is unpaid and upgrad is paid.

When you update a program, you’re applying new patches and changes to the existing file on your computer. The update file you’re downloading and installing is pretty small comparatively, so it doesn’t take long. While the program may look different to you as the end user, it’s usually in a pretty minor way.

When you upgrade a program, then the existing file is being uninstalled, and a new one is being installed in its place. This takes significantly longer, and there are many more chang

What would life look like if your ANNUAL income suddenly became your MONTHLY income ? Imagine that you got a check today for all the money you earned all last year…

Update: is an advisement providing more up-to-date information than currently known.
Upgraded: an improved component or replacement item,

The software update includes bug fixes, and other small improvements, while a software upgrade changes the version of the software.

update is free of cost and upgrade is payable.

update is unpaid and upgraid is paid.

When we perform an update, it involves making changes to an app or an operating system is such a way that it doesn’t affect its core structure. So, most of the frequent changes made to your computer like bug fixes, security patches, adding support for drivers and newer hardware, etc. can be termed as an Update.
When a set of changes made to a software are significant and substantial enough, we can call it an Upgrade.

What would life look like if your ANNUAL income suddenly became your MONTHLY income ? Imagine that you got a check today for all the money you earned all last year…