BMP180 is a pressure sensor from Bosch. Detailed description is here: https://www.bosch-sensortec.com/en/homepage/products_3/environmental_sensors_1/bmp180_1/bmp180
The BMP180 sensor uses I2C protocol to read out barometric pressure values. You need to connect the SDA and SCL pins accordingly (the Arduino's datasheet might refer to this interface as TWI or Wire).
|BMP180 pin||Where to connect|
|GND||Any ground pin (on Arduino)|
|3.3V||3.3V voltage source|
|VIN||If 3.3V not connected, connect to 5.0V|
|SCL||SCL pin on Arduino (for example, A4 on a Pro-Mini)|
|SDA||SCL pin on Arduino (for example, A5 on a Pro-Mini)|