There are different ways to express water salinity. Weight percentage and parts per million (ppm) are two general terms. You can also express in terms of (milli/micro)Siemens.
When we say salinity it indicate saline. Saline is enriched in total dissolved solids and in particular most dominant is NaCl, Desalination is a process to remove NaCl as well as other dissolved cations and anions in which Mg,Sr, B etc. Ultimately reduces total dissolved solids from the water. TDS is directly related with specific conductivity of water. Furthermore, HCO3/Cl is low in saline water. In view of above parameters classification can be made.