Some species of tick are capable of spreading disease to humans (Lyme disease, Rocky Mountain Spotted Fever). Although the infectious agent does not affect the tick, once it is passed through the tick's saliva into the human bloodstream, it can cause an array of symptoms including fatigue, headaches and general malaise. If you suspect you have been bitten by a tick, seeking the advice of a medical professional as soon as possible is prudent.
Ticks are not bugs, they are arachnids, which means they have 8 legs. Some ticks are round (like beans) while others are flat with festoons (folds that look like a ridge) around their abdomen. All ticks are parasitic. Their body shape color can greatly change after a blood meal.