Complex sentence: Extensional tectonics is accomplished by rifting, where the continental lithosphere undergoes horizontal extension, the rock will stretch until faulting occurs and continued tension creates normal faults or systems of normal faults, either horst and grabens or listric faults.
Split into simpler sentences: Extensional tectonics is accomplished by normal faulting or larger scale rifting, where the lithosphere undergoes horizontal extension. The crust will stretch until faulting occurs and continued tension creates systems of normal faults, either horst and grabens or listric faults.