Was your first in-person meeting with your sponsor the first communication you ever had with them?
The question is asking you for the extent of your relationship to your spouse before your first meeting. It is one of several that CIC uses to assess the credibility of the relationship, to look for marriages/relationships of convenience conducted only for immigration purposes. If, for example, you had no pre-meeting contact with your sponsor and married them at your first meeting, that could be a "red flag" prompting further inquiry.
In your case, the extensive relationship history sounds like it would be reassuring rather than a "red flag." However, you may have some trouble if you have not been together since 2008-2010 (I'm not entirely sure of the timeline) without actually being married, since CIC will question whether you have maintained a common-law relationship.