Did you try running the code and looking in the command window? They're making "time" a row vector - a list of 7000 elements uniformly spaced between 0 and 35. And making a row vector called "pla" of 7000 zeros, because 7000 is the length (number of elements) of the vector called time).
And they're not "strings" (characters) - they're numerical arrays of class "double".
