I want ton know how multidrop differ from daisy chain topology? I am using RS 485 standard and modbus protocol for communication. So which topology is best for my requirement ?
They are the same thing in terms of RS-485. Electrically identical. Multi-drop is the more accepted term.
To put a finer point on it, daisy-chaining is a connection technique whereby one RS-485 adapter is wired directly to the next one, and so on.
The alternative connection technique (which would not be called "daisy chaining" is to have a common bus architecture, and just have each adapter connect to the bus).
Daisy chain is a topology of connecting more than one device on a single communication line. Further, there are terms of communication called as half duplex and full duplex. RS485 can be operated in both modes depending on 2 wire or 4 wire configuration.
RS485 is always a multidrop bus which means more than one device can transmit data but not all at the same time. In other words, the bus architecture may be comprised of one master and different slaves but communication will happen only between master and only one slave.