What is the difference between "which are relevant to explaining the discourse functions" and ...

What is the difference between "which are relevant to explaining the discourse functions" and "which are relevant to explain the discourse functions"?

Context:

In this chapter we are concerned with the way clauses are adapted to fit the requirements of communication. The principd syntactic means are:
word order (1 1.2)
the passive (I 1.3)
a existential there (11.4)
a dislocation (11.5)
defting (11.6)
These devices are crucial for making clauses fit in with the context, thereby building a coherent text that conveys emphasis and related stylistic effects where required and eases the processing for the receiver. They may all be seen as means of re-arranging the information in a clause in different ways to achiwe some such purpose (or frequently a combination of such purposes) which other structural options would not in that instance do successfully. Consequently we will, during the course of the chapter, utilize concepts such as the following, which are relevant to explaining the discourse functions of syntactic devices such as those abovc information flow:
given/topical v, new information
focus and emphasis, including end focus and double focus
contrast
intensification