At an everyday scale, yes: you are touching the chair. At the atomic scale, however, the idea of solid surfaces meeting is more subtle. Atoms contain negatively charged electrons around positive nuclei. When the electron clouds of atoms in your body approach those in the chair, electromagnetic interactions and quantum effects strongly resist further overlap. That resistance produces the contact force supporting you. Your atoms do not need their nuclei to collide with the chair's nuclei for you to feel a solid surface. So 'touch' is really an interaction between matter through forces at extremely small scales.

The useful part of this physics is that it helps people predict and design real things. Engineers often begin with the same simplified model used in school, test where it works, then add more detail when measurements show that the real situation is more complicated.

The motion can be understood by adding the forces as vectors. If they balance, the resultant force is zero and the object stays at rest or continues at constant velocity; if they do not, it accelerates. Friction and drag transfer energy to the surroundings, usually as heating, so maintaining a steady speed can still require continuous work even when the speed itself is not changing.