In the Controls Bar you have your Transport buttons, Time Display, Tools and Toggle buttons and account Login/Logout button.
Use the Time Display to change your song tempo and time signature. Click the left part of the display to change view between time in seconds or bars & beats.
The Transport has controls to control playback of your project, to record and activate metronome and input monitoring.
Back to start, playhead is returned to the start of the arrangement.
Play or Pause playback.
Start recording on the record enabled Tracks.
Turn the loop locators on/off to repeat that section in the arrangement.
Turn the metronome on/off. Right click to quick access studio settings.
Turn input monitoring on/off.
Tools are used to move, manipulate or edit things within the arrangement and content editor.
Arrow Tool, mainly used for selecting, moving and resizing regions and notes.
Pen Tool, used for drawing new regions in arrangement and notes in the Piano Roll.
Time Tool, mainly used to stretch audio and note regions.
Split Tool, used to split regions and notes in arrangement and Piano Roll.
Toggle buttons are used to open and close different parts of the studio interface.
Open and close the Master Track in the Track Panels area.
Open and close the Content Editor.
Open and close the Virtual Keyboard.
Open and close the Track Inspector.
Open and close the studio Sound Library.