“在线” means “online,” and “等” means “to wait.” This term, often used in online conversation, literally means “I’m waiting for an answer right here online,” which implies that the subject matter is very urgent and the speaker wants an immediate answer.
Wǒjiā háizi kēxué kè yǒu xiàng rènwù shì yǎngcán，nǐ zhībuzhīdào nǎlǐ kěyǐ mǎidào cán hé sāngyè？Zàixiànděng。
My kid has to raise silkworms for his science course. Do you have any idea where I can get silkworms and mulberry leaves? This is urgent.
Wǎngshàng kěyǐ mǎidào，rúguǒ bú fàngxīn zhìliàng，kěyǐ qù xuéxiào fùjìn de xiǎo shūdiàn kànkan，hěnduō diàn dōu yǒu。
You can buy them online. If you are not sure about the quality of online purchases, you can try the small bookstores near schools. Most of them have it in stock.