Product involvement, quite intuitively, can be of two types:
High: Product involvement by customers is high for products that customers perceive to be highly valued i.e. may have a higher cost or may have long term benefits and bought after careful consideration. For example, a car would be a high involvement product as it is expensive and bought after much research.
Low: On the other, low involvement products are those that are bought on a day-to-day basis and become more of a habitual buy. These products are generally cheaper and do not call for in depth research. For example, a toothpaste tube would be a low involvement product for general masses as it is bought in fixed intervals (say every month) and does not cost huge sums of money.