In the English language, only is one of the most misused modifiers imaginable. Most of the time, we native speakers just "get it" in terms of what the writer means in his or her placement of only in a sentence. In formal written text, however, there can be a difference between, for example, "We only sell red socks" and "We sell only red socks." In legal documents, lawyers, for instance, may be a bit more careful in its usage.
Have a look at what rules can apply to a little word such as "only."
1./ Only I love my wife. [Only is an adjective.]
2./ I only love my wife. [Only squints. It can be either an adjective modifying I or an adverb modifying love.]
3./ I love only my wife. [Again, only squints slightly.]
4./ I love my wife only. [An adverb modifying love.]