What do you understand by a profiler with reference to MongoDB?

A database profiler is something which collects fine-grained data about write operations of MongoDB, the cursors, and the database commands. Profiling can be enabled on a per database or pre instance basis. When profiling is enabled, the profiling level also gets configurable. By default, the profiler will be off. All the data collected by the system.profiler collection is written by the database profiler to it. This collection is a capped collection. 0, 1, and 2, these are the three levels available in the database profiler. Profiling in a database can be enabled from the mongo shell or using a profile command through the driver. While enabling profiling, profiling level is also set. The profiler is used to record data in the system.profile collection.