Bonsai is just a tree in a pot, to be more specific, a bonsai is a miniature representation of a full grown tree cultivated in an aesthetically compatible container.
Any species of tree has the potential to be a bonsai although some are better than others. A misconception is that dwarf varieties make the best ones but this is not the case as they are often weak growers and easy get disease. The foliage needs to match the scale of the tree.developing a bonsai takes a long time and discipline: daily watering regular, feeding, trimming, repotting, wire-training and root care.
Beech, hawthorn, pine, larch and elm make fine bonsai so do many garden shrubs. Bonsai are among the best cared- for plants in cultivation and often out live their full size counterparts.
The picture below is my oldest and first Bonsai tree it is a maple, and my favorite.
I have always had a problem with it even though it is my favorite, no matter what i do i can not get the leaves to reduce in size i have tried for many years , last year i lost a few branches so i have put it back into a larger pot for now to redesign it and hopefully get back the branches i lost. I will take a photo of it at a closer angle so you can see what i mean.
At the moment i have it on the edge of my pond and it looks good even though the leaves are still huge.
Of course my other passion are my Bonsia, i have been growing for many years mainly small as i have not always had the space, over the next few weeks i will post some pics of my plants. to share i am a member of many groups and through trail and error of which over the years i have had many errors and have learnt from these if you have any questions please feel free to ask.