The free transform tool is one way of manipulating one part or area of your content. This tutorial explores the actions of entering transform mode, re-sizing or stretching the selection, rotating the selection, making specific transformation, and alternatives.

Entering transform mode

Select the necessary layer or selection from the layers palette, then go to Edit > Free Transform in the Menu bar. The shortcut is Command-T. A square box with smaller boxes will appear around the layer. The smaller boxes are called handles. Once the box appears, transform mode is activated and other functions of Photoshop will be inaccessible.
To cancel the transformation at any time, press the Escape key or click the crossed-out icon in the Options bar.

Re-sizing or stretching the layer/selection

Click and drag either a corner or edge handle.
Each corner handle allows the layer to be transformed diagonally in any direction.
Each edge handle increases the width or height of the layer accordingly.
TIPS :
1. Holding the Shift key while dragging a corner handle will increase the size of the layer with respect to the opposite corner, while retaining the layer's original proportion. Holding Shift only works on the corner handles.
2. To increase the size and proportion with respect to the layer's center, hold Shift+Option.

Rotating the layer/selection

Move the mouse just outside a corner handle and the customary arrow-mouse icon will appear as a rotation icon.
Press and hold the mouse while dragging around the center of the layer to notice how the layer rotates.
TIP: Holding the Shift key while performing this action will rotate the layer in 45 degree increments.

Making specific transformations

Enter an exact size in the Options bar located at the top of the screen. While the transformation box is visible, a value in any unit or percentage may be inputted to scale the layer to a desired size.

TIP: To maintain the layer's proportion, click the icon that looks like a chain link.

Transforming a selection

Instead of transforming the content of a selection, it is also possible to transform the outline (area) of the selection. To do this, go to Select > Transform Selection. All of the above transformations can be performed on selection areas.

Alternatives

Instead of entering the transform mode each time, checking the "Show Transform Tool" while using the Move tool will create a transform box around any layer(s) selected from the layers palette. All the same transformations can be made in the same way. Additionally, if multiple layers are selected at once, a transform box will appear around all the layers.

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