Taoism consists of philosophy, religion, and practice. The Tao is the mysterious force that guides all things, it is what came before heaven and earth, and from it comes all of creation through the mixing of yin and yang or the male and female energies. It cannot be understood by the mind, but it can be experienced and known intuitively. Everything emerges from the Tao, and eventually everything returns to it - we are the waves and it is the ocean.
The philosophical side of Taoism is about understanding different ways in which we can live a more harmonious life, by flowing with life rather than against it. The Tao Te Ching emphasizes virtues such as humility, flexibility, softness, non competitiveness, limiting one's desires, and becoming like a child again -- which leads a person to living a content and happy life.
The practical side of Taoism includes things such as Tai Chi, Chi Kung, and Taoist Yoga. These are ways of getting in touch with the life force energy, Chi, which is present in each and every thing. Taoists believe that sickness is caused by blocked chi in the body, and that the optimal condition is to have our chi flowing through our body unobstructed, and the aim of Chi Kung is to guide and circulate this Chi through the body so the overall functioning of one's system is strengthened and enhanced. Tai Chi is considered a soft martial art applied with the internal power of Chi, which applies the laws of yin and yang in its actions. Taoist Yoga is concerned with attaining spiritual immortality/enlightenment and longevity.
I probably wouldn't go into the religious side of it, but I might mention the two common schools - Highest Clarity which was popular in the Tang dynasty who's emphasis was on personal cultivation and spiritual development, and the school of Complete Perfection which is a monastic school that synchronizes teachings of Daoist cultivation of the body, Buddhist meditation, and Confucist ethics, and practices Inner Alchemy to attain spiritual immortality.
Although that would all have to be said over a tea or coffee
. In short, Taoism is about finding harmony and balance in one's life, and cultivating the qualities that help a person attain this balance.