It's easy to place videos on a website that play after downloading. It's tougher to build true streaming. This means that your video plays as it downloads. This is a better experience for your visitor since they won't have to wait for a huge video file to download before viewing. It also conserves bandwidth.
The easiest approach is to embed a You Tube or Vimeo video in your webpage. The You Tube branding may not be ideal for many situations. I've also found some delays in their code that can cause your page to load slowly if the embedding is done incorrectly. The best approach is to host your own streaming server. In the past, this was extremely expensive. We've been using a system built on Amazon Web Services to host video with network quality results and easy on the budget. The initial setup is somewhat complex, but once it's up and running, we've found it to be fast and reliable.
We'll be happy to discuss this with you and can add streaming video to a site you already have or add it to a site we are building for you.