You can see Basics of skeching parameters and sketching constrains in these links:

https://help.autodesk.com/view/fusion360/ENU/courses/AP-SKETCH-BASICS-PARAMETERS?wvideo=9i0e7f28gd

https://help.autodesk.com/view/fusion360/ENU/courses/AP-SKETCH-BASICS-CONSTRAINTS

Also, link: