Traceroute reading

[agringaus]

What do the dashes mean in the empty rows of some hops? Is it because the target server did not respond as traceroute expected and a timeout occurred?
example: https://webpagetest.org/result/200218_Q4...b80e0b6de/

Also, from testing of one large object of 6MB I noticed that sometimes it downloads only part of the image content 300KB. Is packet loss possible because of a timeout?
Thank you.