1(lit.) the rise and fall of the terrain (idiom)
2(fig.) the whole sequence of events; causes and effects
Example
suī rán虽然wǒ我zhǐ shì只是zài在wǎng shàng网上kàn看le了jǐ几zé则xīn wén新闻，dàn但yě也dà gài大概zhī dào知道le了zhěng整jiàn件shì事de的lái lóng qù mài来龙去脉。
虽然我只是在网上看了几则新闻，但也大概知道了整件事的来龙去脉。
I'm only reading the scraps on news on the Internet, but, well, I get the general picture.