The smallest of the Embraer corporate jets is a bit of a crossover between the Cessna CitationJet and the Raytheon Premier I. Compared to the first the Phenom has a more pointy, streamlined nose, smaller cockpit windows and large dorsal fin. The Premier I also has a pointy nose, but difference cockpit windows and swept wings. 

Note that the Phenom 100 has a larger brother, the Phenom 300, with which is shares a large resemblance. The Phenom 300 has however swept wings with winglets and is longer, with five cabin windows instead of four.

There are four versions, which as externally the same. The Phenom 100 is the baseline version. A different spoiler system on the wings is the main characteristic of the Phenom 100E. The Phenom 100EV (for Evolution) has a better performance due to weight savings and a higher thrust setting for the engines. Finally, the Phenom 100EX has a lighter interior, updated avionics and a (fifth) side facing seat as standard. The latter was optional on other previous versions though...

In Brazilian military service the Phenom 100EV is designated as U-100. The Royal Air Force calls them Phenom T1.