A variety of resistance exercises can be used to train the pectoralis major, including bench pressing (using dumbbells, barbells or machines at various angles such as decline, incline and flat where the hips are above, below and level with the head respectively), push ups, flyes (using dumbbells or machines at either flat or inclined angles), cable crossovers or dips. Multi-joint press exercises are better for building muscle mass, while fly and crossovers are more suited for shaping and increasing striations. This muscle is often said to consist of four portions (upper, lower, inner and outer) but the pectoralis actually contracts evenly across all heads during most exercises and as such no portion can be 'targeted'.
How much of this is true?
I do incline presses because I want to buff out the upper part of my chest (pectoralis major), but if it doesn't really matter (either the muscle contracts or not), is there a point? How does this carry on to other exercises?
Look at all the people with small rear delts in relation to their front delts and the deltoids are considered one muscle. You can target different parts of a muscle because muscle has mutliple innervation points.