What constitutes a competitor, and what is the goal you have in mind when you conduct competitor analysis?

Thanks for asking this question. The exercise of defining your competitive set is a critical, but at times under-emphasized aspect of conducting research. There are three primary modes for competitive research: 1) optimization, 2) growth and 3) exploration.

1) Optimization is the most narrow mode. This is meant to identify how you are positioned relative to direct competitors, who are in the same industry and product family as your company. This is where your win/loss interviews become important.
2) Growth mode is where you would look at direct and indirect competitors, who may share an industry, but are in a different product family or vice versa. The goal here is to understand how to expand your addressable market and seek product adjacencies.
3) Lastly exploration mode is the widest lens. Here I focus on the customer jobs to be done. Anything that enables the customer to achieve that job (the substitutes) can be informative on customer barriers to entry for the most difficult prospects to acquire and provide a source of ideas for exploration of new business verticals. These substitutes may be in the informal economy (such as borrowing from a friend or hitchhiking) depending on the industry that you are in.

All of these are important. Depending on where your company is in its growth cycle it may need a different balance of each. For example, very mature companies may focus on exploration and growth mode, while new entrants may focus primarily on optimization and growth.