ae: Aggregated Ethernet A virtual aggregated link.
as: Aggregated SONET/SDH A virtual aggregated link.
at: ATM1 or ATM2 IQ Asynchronous Transfer Mode
cau4: Channelized AU-4 IQ Configured on the Channelized STM-1 IQ PIC.
coc1: Channelized OC-1 IQ Configured on the Channelized OC-12 IQ PIC.
coc12: Channelized OC-12 IQ Configured on the Channelized OC-12 IQ PIC.
cstm1: Channelized STM-1 IQ Configured on the Channelized STM-1 IQ PIC.
ce1: Channelized E1 IQ Configured on the Channelized E1 IQ PIC or Channelized
STM-1 IQ PIC.
ct1: Channelized T1 IQ Configured on the Channelized DS-3 IQ PIC or
Channelized OC-12 IQ PIC.
ct3: Channelized T3 IQ Configured on the Channelized DS-3 IQ PIC or
Channelized OC-12 IQ PIC.
cp: Collector Configured on the Monitoring Services II PIC.
ds: DS-0 Configured on the Channelized DS-3 to DS-0 PIC, Channelized E1 PIC, Channelized OC-12 IQ PIC
dsc: Discard Allows you to identify the ingress point of a denial-of-service (DoS) attack.
e1: E1 Includes the channelized STM-1 to E1 interfaces.
e3: E3 Includes the E3 IQ interfaces.
es: Encryption Allows you to configure a security association (SA) name
with a logical interface.
fe: Fast Ethernet 100Base-TX (Fast Ethernet, 100 Mbps).
fxp0: Management and internal Ethernet The management Ethernet interface is an out-of-bandmanagement interface within the routing platform.
fxp1: Interface that connects the routing engine and packet forwarding engine.
ge: Gigabit Ethernet Includes Gigabit Ethernet IQ interfaces.
gr: Generic Route Encapsulation tunnel Allows you to configure a unicast tunnel using GRE
encapsulation.
gre: Internally generated This interface is internally generated and is not
configurable.
ip: IP-over-IP encapsulation tunnel Allows you to configure a unicast tunnel using IP-IP
encapsulation.
ipip: Internally generated This interface is internally generated and is not
configurable.
lo Loopback This interface is internally generated. The logical
interface lo0.16383 is a non-configurable interface for routing platform control traffic.
ls: Link services Supports bundles that contain links.
lsi: Internally generated This interface is internally generated and is not
configurable.
ml: Multilink Includes Multilink Frame Relay and Multilink PPP.
mo: Monitoring services Includes the monitoring services and monitoring services
II interfaces. The logical interface mo-fpc/pic/port.16383 is an internally generated, non-configurable interface for routing platform control traffic.
mt: Multicast tunnel Internal routing platform interface for VPNs.
mtun: Internally generated This interface is internally generated and is not
configurable.
me0: – out of band management interface on ex switches
oc3: OC-3 IQ Configured on the Channelized OC-12 IQ PIC.
pe: This interface is present on the first-hop routing platform. Encapsulates packets destined for the rendezvous point (RP) routing platform.
pd: This interface is present on the RP De-encapsulates packets at the RP.
pimd: Internally generated This interface is internally generated and is not
configurable.
pime: Internally generated This interface is internally generated and is not
configurable.
rlsq: – a redundant bundle interface, made of two or more lsq interface. If you have redundant AS Pics.
se: Serial Includes the EIA-530, V.35, and X.21 interfaces.
so: SONET/SDH Both are widely used methods for very high speed
transmission of voice and data signals across the numerous world-wide fiber-optic networks.
sp: Adaptive services The logical interface sp-fpc/pic/port.16383 is an
internally generated, non-configurable interface for routing platform control traffic.
t1: T1 Includes the channelized DS-3 to DS-1 interfaces.
t3: T3 Includes the channelized OC-12 to DS-3 interfaces.
tap: Internally generated This interface is internally generated and is not
configurable.
vcp: – virtual chassis interface (EX4200 only)
vsp: Voice services The Adaptive Services (AS) Physical Interface Card (PIC)
supports the compressed real-time transport protocol (RTP) on this interface.
vt: Virtual loopback tunnel On routing platforms equipped with a Tunnel PIC,
enables egress filtering.
xe: – 1GE optical interface on ex switches

Juniper reference:
http://www.juniper.net/techpubs/software/nog/nog-interfaces/download/nog-interfaces.pdf