Yes each of the three line you press enter.
The first line sets permissions in the extensions folder.
The second line removes the extensions.mkext
The third line repairs permissions to the entire drive.

Drivers "kexts" are stored in the extensions folder. OSX creates a cache file called Extensions.mkext of all the appropriate drivers. What we are doing is adding a new driver, repairing permissions and deleting the cache file so that OSX is forced to create a new one with the new driver.
The reason that we have to use line 1 and line 3 is that repairing permissions only works with Apple kexts. OSX does not know what permissions to set thirdparty/homemade kexts to so we use the 1st line.

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