What is the Difference Between IPS and APP?

I am currently exploring the differences between IPS and APP, specifically in the context of securing HTTPS servers. Here is my rule for testing:

#For APP, working good at http, a lot of ip not blocking in https. F-SBID(--name "Http 403"; --pattern "403 forbidden"; --protocol tcp; --no_case; --flow from_server;)  #For IPS, both http & https are working good. F-SBID(--name "Http 403"; --pattern "403 forbidden"; --protocol tcp; --no_case; --flow from_server,reversed;)

1. IPS and APP can use the same syntax. If I want to protect an HTTPS server, should I use IPS or APP?

2. Have any more details about IPS and APP?

3. Looks like App have issue for https traffic, maybe is bug?