It's the frequency at which you can get a measurement from the device. It will take a finite time for a measurement to be realised in any device and could be to any number of physical reasons: the time the device to reach temperature or pressure, any period for the device to clear down and set its registers to reflect the new measurement, the time for the I2C bus to re-set and prepare for the data to be read and so on.
The BMP085 has a number of digital registers that have to be read and then the pressure value calculated. There are a set of registers associated with temperature and a further set associated with pressure, these are all read down a single pair of wires using i2c. There are also some calibration coefficients to be read that are specific to each device which have to be read by your software prior to calculating real values.
Take a look at page 13 of the datasheet at
https://www.sparkfun.com/datasheets/Com ... 000-05.pdf which gives the code required to realise the physical quantities of temperature and pressure. It looks involved but its not really, just take your time and don't panic! Recognise that the data is spread over two bytes and these parts have to be combined within your code before you start processing to get real values. There are code examples out there, try searching 'Arduino bmp085' for example, older examples tend to expose the raw processing a little more easily (perhaps).
Hope this helps.