TRANSFORM

One of the most useful commands in Photoshop is Ctrl + T or Transform.
Another way to reach Transform is by going to the Edit menu.
Ctrl + T will create a bounding box around the object in the layer you have selected when you use this command. It allows you to reshape and reposition the object in a variety of ways.
To get out of the bounding box – hit ESCAPE key
To Apply a transformation :
1) double click inside the bounding box
OR
2) hit ENTER
With Free Transform you can do a number of things:
1) Scale an Object Proportionately. Hold down SHIFT and pull the box from a corner. This will up scale or down scale the object proportionately
2) Scale an Object. Grab a side of the box to lengthen or widen the object
3) Rotate an Object. Move the cursor outside the bounding box and it will turn into a double curved arrow. This option allows you to rotate the object. You can move the registration point at the center of the object to another location and the object while in rotation mode will rotate from that point.
4) Flip Horizontal or Vertical. Right click inside the bounding box to see the options for Flip Horizontal or Flip Vertical. Choose one or the other and watch what happens.
5) Skew. Hold down the Ctrl key as you pull on one corner of the bounding box. This will distort or skew the object.