Vapor vs Forge ?

Have you read some of the documentation for vapor, the docs will clear up these questions.

https://docs.vapor.build/1.0/introduction.html

I have read them before but still having an issue understanding when to use vapor and when to use forge.

Some of the big differences:

Vapor:

• Instant scalability (both ways, it will meet your customer demand, and save you money on quiet days)
• No infrastructure worries - just focus on the app & code
• Regional data regulations are easier to handle
• Small learning curve. It is different. Deployment won't happen from GIT without you setting it up (e.g. GitHub actions). Serverless means no storage, so you'll need to get used to working with S3. Vapor uses CDNs (automatically) for static content, which means a few little optimizations.
• Set up of databases, domains, storage, caching, queues etc all done for you.
• Fantastic API

Forge / Ploi / Other

• Also easy
• Totally configurable environment
• low cost and yet performant, up to a ceiling.
• Predictable costs
• All of the workings are up to you. Probably fine (with e.g. Forge) but it depends on the complexity of the project, criticality, any data reg rules applicable, and your skill. e.g. Security & maintenance.

Cost differences can be large. You could host a small project on a $5 linode. Starting costs, all things considered, with Vapor are around $50pm, BUT that reduces per-project the more projects you host on Vapor. So if you have any significant deployments, or value the scalability/featureset, then you're likely to quickly see returns here.

Vapor is suitable for all applications except static sites.

Vapor and Forge are in some ways in competition with each other, but also serve different needs. I don't see why one one "take the place of the other" going forward.

Which one would I use? It depends on the project. But, I have switched almost all projects to Vapor and use S3, Netlify and Firebase for static hosting just because.