Canon EFS 18-55mm f3.5-5.6 IS is a great lens to start of with to learn the basics but also a great backup lens but mostly its a great lens for several occasions: Night Party Events, Landscapes, portraits, tight spaces or wide angle on a steadicam. Also mostly when there is a new camera you want to buy and sell your old camera, it is easier to sell it with a lens then the body only and also you get much more than when you are just selling the body only.
The lens brand new cost around 100 to 200 euro but I would advice to look for a secondhand mostly 2nd hand you can easily find decent almost brand new ones, because allot of new models are sold with a kitlens instead of body only and the people sell of the lens pretty fast for prices around 75 to 100 euro. However dont be fooled by the old version without the Image stabilization which you can buy for 25 to 50 euro second hand.
For filming with this lens is a nice wide angle, I use to own 18-200mm by Sigma but found that I only used that lens for it being wide and not for it zoom, also because the aperture was to slow when you zoom in while I do more night photography instead of daytime. However for day time it is better to have a larger range, because in open space you can get nice shots from a distance and the 55mm might not be far enough of a zoom. However for filming the f5.6 is not a nice aperture to use for a nice film looks so you might want to consider buying a nicer 50mm lens with a much faster aperture.
The focal length is 18-55mm however it is an EFS and only fits for a crop camera and the actual focal length on a crop compared to a full frame are actually different numbers. 18mm is comparable to a 28mm and 55 would become a 88mm on a crop sensor.
Conclusion is to keep the lens just for when you want to change from body its easier to sell your camera. However if you are able to get a decent cheap secondhand one and find a new body it might be a nice cheap option then buying a new set.