Workflow Designer allows you to work with a number of conditions for setting up branching in a workflow based on the if/else logic. Essentially, this means that based on the result of the condition, the workflow can be branched to perform different operation for each result. Internally, if you review the XOML file created for the workflow, you see that all these conditions are actually rules-based conditions (defined in the .xoml.rules file) used by the IfElseActivity activity.
SharePoint Designer workflows in the current release aren't capable of looping through the actions. This means that you can't emulate a For-Loop or a Do-While logic by using SharePoint Designer workflows.
Defined by the description "If field equals value," this condition can be used to compare a field in the SharePoint list or library with a constant or a value from anther field or workflow variable. The description has three hyperlinks:
Field: This is a dropdown menu that can be used to choose any of the fields/columns in the list of library.
Equals: Shows a dropdown menu that can be used to choose an operator for the comparison. The dropdown menu has the following operators: equals, not equals, is empty, is not empty, begins with, does not begin with, ends with, does not end with, contains, does not contain, matches regular expression, equals (ignoring case), and contains (ignoring case).
Value: This can be ...