Throughput in performance testing is the no of transactions
that can be handled simultaneously.It can be tested using
automation tools.

through put means number of hits per second ,and it can be 
tested by using LoadRunner

performance testing:testing the stability and response time 
of an application by applying load

response time:time taken to recieve request ,execute and 
send programm
t=t1+t2+t3
t1,t3=depends on request
t2=depends on code
 
stability:with stand load

generaly we are using performance tools such as
astro load
load runner
silk performer
rational performer
eload
web application stress
i metrica

Through put is the kind of performance testing.It refers to
the number of client requests processes within a certain
unit of time. Typically, the unit of measurement is requests
per second or pages per second. from a marketing
perspective, throughput may also be measured in terms of
visitors per day or page views per day.


we can measure this using automation tools like Load runner..

Throughput is one of the basics performance metrics. It is 
the rate at which a computer or network receives data or 
request per sec. Tipically it's expressed like bytes/sec.

So, if the throughput is increasing for increasing load 
then the applications i performing well.

Remember that it's not the only one performance metric. You 
can measure it with LoadRunner, but this is not the only 
one tool in the market.