Statistics:

With the -statistics option, ip also prints interface statistics:

kuznet@alisa:~ $ ip -s link ls eth0
3: eth0: <BROADCAST,MULTICAST,UP> mtu 1500 qdisc cbq qlen 100
    link/ether 00:a0:cc:66:18:78 brd ff:ff:ff:ff:ff:ff
    RX: bytes  packets  errors  dropped overrun mcast   
    2449949362 2786187  0       0       0       0      
    TX: bytes  packets  errors  dropped carrier collsns 
    178558497  1783945  332     0       332     35172  
kuznet@alisa:~ $

RX: and TX: lines summarize receiver and transmitter statistics. They contain:

• bytes -- the total number of bytes received or transmitted on the interface. This number wraps when the maximal length of the data type natural for the architecture is exceeded, so continuous monitoring requires a user level daemon snapping it periodically.
• packets -- the total number of packets received or transmitted on the interface.
• errors -- the total number of receiver or transmitter errors.
• dropped -- the total number of packets dropped due to lack of resources.
• overrun -- the total number of receiver overruns resulting in dropped packets. As a rule, if the interface is overrun, it means serious problems in the kernel or that your machine is too slow for this interface.
• mcast -- the total number of received multicast packets. This option is only supported by a few devices.
• carrier -- total number of link media failures f.e. because of lost carrier.
• collsns -- the total number of collision events on Ethernet-like media. This number may have a different sense on other link types.
• compressed -- the total number of compressed packets. This is available only for links using VJ header compression.

If the -s option is entered twice or more, ip prints more detailed statistics on receiver and transmitter errors.

kuznet@alisa:~ $ ip -s -s link ls eth0
3: eth0: <BROADCAST,MULTICAST,UP> mtu 1500 qdisc cbq qlen 100
    link/ether 00:a0:cc:66:18:78 brd ff:ff:ff:ff:ff:ff
    RX: bytes  packets  errors  dropped overrun mcast   
    2449949362 2786187  0       0       0       0      
    RX errors: length   crc     frame   fifo    missed
               0        0       0       0       0      
    TX: bytes  packets  errors  dropped carrier collsns 
    178558497  1783945  332     0       332     35172  
    TX errors: aborted  fifo    window  heartbeat
               0        0       0       332    
kuznet@alisa:~ $

These error names are pure Ethernetisms. Other devices may have non zero values in these fields but they may be interpreted differently.