Thats what we call the Contextual Toolbar. This toolbar appears when you click on any object on the drawing canvas. All the commonly used operations of an Object are available right here, where and when you need then.
Contextual Toolbar for a single object

Contextual Toolbar for multiple selected objects

Text Edit button
The first button on the Contextual Object toolbar is the Text Edit Button. This reveals the Text Edit Bar and is used to enter and edit text in the selected object. Read more about working with the Text Edit Bar to style, position and link text.

Create Connector button
The second button on the Contextual Object toolbar is the Connector button. This provides easy creation of connectors from the selected object to any other object on the canvas. Read more on Working with Connectors.

The Order Objects button
The third button is the Order Objects button. This lets you adjust the Z-levels of the object either bringing it to the front or sending it to back behind another object.
Clicking on the Order Object button reveals a sub-menu with the following options:

1-Click Create & Connect button
The final button on the Contextual toolbar is the special 1-Click Create & Connect button. This button exhibits different behaviours depending on the type of diagram being drawn. Shown here on a basic Square shape, the default behaviour is to create a duplicate of the selected object and connect up the 2 objects. Refer to 1-Click Create & Connect for advanced use cases.

Group button
The first button on the toolbar for multiple selected objects is the Group feature. Clicking this will group all the selected objects. Groups can then be minimised and behave as a single object.

Align Objects button
The Align objects button aligns the selected objects along any of the given axis.

Distribute button
The Distribute feature automatically distributes the selected objects either vertically or horizontally depending on the selection.

Match Size button
Use this button to evenly match the heights or widths of the selected objects with just 1-click.
