[R] help regarding levels

[K3]

When i try to extract a column of data from an excel file and assign
it to a variable , say x, it does assign the column of data as well as
different levels.
it looks something like this when i print.

[1] 6.91 5.89 7.44 8.82
80 Levels: 1.43 102.07 103.65 106.21 106.24 107.15 108.58 11.19 ...

so how does this levels come into picture and what do they do. I
couldnot run linear regression with x as a predictor just because of
this levels. please explain.