The microphone you use is but one of many factors that affect the quality of your audio recordings.
Recording on a desktop / laptop computer
The microphones built-in to desktop/laptop computers typically sound poor, and capture a lot of echo from the room. This is because they are designed to capture audio coming from a wide range of angles and distances.
A good external microphone will dramatically improve the quality of your audio when recording on a desktop/laptop computer.
We recommend purchasing an entry-level USB condenser microphone for around $50, such as the Blue Snowball iCE or Fifine K669B.
Recording on a smartphone
The microphones on smartphones are much better than desktop/laptop ones, as they are designed to be placed near the mouth and capture a person's voice. It's usually unnecessary to add an external microphone to a smartphone. The best results can be had by speaking closely to the in-built microphone on the device.
Many Bluetooth earbuds/headsets like Apple AirPods have microphones built-in. However, these are located far from the mouth so the audio can sound muffled. Additionally, the Bluetooth connection can be unstable, and any drop in connection will create unwanted sounds or silences in the audio recordings.