Chen style is the oldest of the five major styles of tai-chi chuan with all of the other styles having been derived from it. Yet it is also distinctly different, containing elements that are not present in the other styles.
Chen style tai-chi can be characterised by its' spiral movements, speed changes and explosive energy releases (fa-jing). Traditional Chen style can generate substantial heat in the body and feels simultaneously invigorating and powerful yet calm. The constant winding and unwinding of the spiral movements can clearly be felt reaching deep inside the body, gently stretching tendons and opening joints but this can also put an additional strain on the knees in some of the more extreme movements of the advanced forms.
The Loajia yi lu (old frame, first path) contains about 75 movements (depending on how you count them) and is one of the oldest known tai-chi forms. It is about 200 years old but is thought to be an amalgamation and evolution of several c. 350 year old forms devised by Chen Wang-Ting and the movements contained within may well be older than that. There is also a Xiaojia yi lu (Small frame, first path) and the dynamic Jinjia yi lu (new frame, first path) which are derevations and evolutions of the Loajia and are a similar length. All the slow forms of all 5 major tai-chi styles (together with those of most other styles) can be traced back to the Loajia yi lu.
Other forms in the Chen system include both old and new frame versions of the fast form known as the "pao chui" (canon fist) or "er lu" (second path), a sword form, broadsword, double broadsword, spear, halberd, double sword and staff. Chen style tai-chi is one of the most form-rich martial arts.
Recent developments of Chen style have produced shorter, less demanding forms that are frequently taught to beginners but which still retain the essential characteristics of the original system.
The first of the following YouTube clips is a short demonstration by Grand Master Chen Xiao Wang. He starts by demonstrating the opening movements of the laojia yi lu (old frame, first path), in the middle section he shows the movements of the Jinjia yi lu (new frame, first path) before moving seamlessly into a sequence of fa jing's indicative of the er lu (second path); thereby giving a flavour of all the empty handed Chen forms. In the second video he demonstrates the complete Loajia yi lu.