A musician who plays the violin is called a 'violinist' or, more traditionally, a 'fiddler'. There's one very famous fiddler from history you might know, but he's not exactly in an orchestra.
The Sydney Symphony Orchestra has 29 violinists amongst its ranks—and that's not including their fellow violists!
The plural of cello is either celli or cellos. Also, cello is just a nickname—their full name is actually violoncello, which translates to "small big viola". Instead of resting them beneath the chin, cello players hold their instrument between their legs. This is because they are so big and heavy!
Their bold, rich sound makes up the deeper end of the orchestra, along with the double bass. Can't name a cello piece off the top of your head? You're probably familiar with this one.