determining meaning of basic biological keywords about C. elegans
Have you discovered wormbase yet? It will become your new best friend. In worms gene names reflect the loss-of-function (lf) phenotype. Daf means "abnormal DAuer Formation," so daf-2 was the second daf gene identified (ref). The mutations are called alleles and each worm lab has their own allele designation. e was for England and in that lab's strain list the daf-2 allele was the 1,370th on their list. So daf-2(e1370) designation means that the strain carries a lf mutation in the daf-2 gene, and the specific allele is one that was isolated in Cambridge, UK. I believe that allele is temperature-sensitive (ts) dauer-constitutive.
So at 25⁰C 100% of the animals were dauers. That is when they harvested RNA. It is the entire transcriptome. It sounds like you may be familiar with modENCODE Data Warehouse. You can still ask questions about modENCODE datasets at help@modencode.org. While the modENCODE Data Coordination Center was mothballed at the end of the NIH funding period, there are a few people who still field queries like yours, to the Helpdesk. Also, moving forward the new ENCODE DCC has taken over curation of archival modENCODE metadata.