The specification of IP cameras is quite complicated as most of the features are technical.  We attempt to compare features of the ACTI brand of industrial grade IP cameras here rather than explaining technical features. 

Megapixel refers to 1280 x 1024 dot resolutions of the image quality, otherwise 64x480 if not Megapxiel.  4 = 4Megapixel 
POE stands for Power over Ethernet
D&N stands for Day & Night vision of the camera
IRL stands for Infra Red LED integrated in the camera
VF stands for Variable Focus (normally from 3.3-12mm, otherwise fixed at 4.2mm)
VF(Z) means optical zoomable from the server end
OD stands for out door with Protection against Ingress of Moisture and Dust IP66
VP stands for vandal proofing with hardened glass housing
PTZ stands for panning, tilting and zooming

Model     IP   Mega POE D&N  IRL   VF   OD  VP    Shape

CK5211E   v     (4)    v     v             (Z)    v     v      Box
CK7211    v     (4)    v      v            (Z)     v     v     Dome
CA7411    v      v      v      v             v      v     v     Dome
CA1231    v      v      v      v      v     v      v            Bullet
CA3511    v      v      v      v      v     v                    Dome
CA1511    v      v      v      v      v     v                    Bullet
CA3411    v      v      v      v                                  Dome
CA3401    v      v      v                                          Dome
CA4201    v      v      v                                          Cube
CA4200    v      v                                                 Cube
CA4000    v                                                         Cube
CA8201    v      v      v                                          PTZ
CA8211    v      v      v     v     v                             PTZ

T-series introduced in year 2010 adds 3 functional enhancement to the above IP Megapixel models whilst retaining all other functions shown for the corresponding models.  Please visit the page entitled T-Series IP Camera for a bit more information.

1. H.264
2. Dual streams with the same or different compression (H.264, MPEG4, MJPEG)
3. Wide Dynamic Range

K-series introduced in year 2011H2 extends the feature set to 4Megapixel and Optical Zoom