Task names give you quite a bit of information. There have been a number of questions on the boards which knowledge of task names would have answered in part or even completely in some cases. I am more than happy for other moderators to add to or correct anything I get wrong.

wah2_sam50_a002_201312_25_885_012039265_2 Weather at home version 2 tasks are for Windows only.
a002 is the task number in the batch.
sam50 describes the region (South America) and the resolution used. This one divides the region into 50Km squares. There are also tasks with a higher resolution that use 25Km squares (sam25) Other regions include anz -Australia and New Zealand, safr -South Africa etc. Regions are not all the same size so some take longer than others to complete a model month. The higher resolution models also take longer.

201312 gives the year and starting month the model is looking at. December 2013 in this case.

25 is the number of model months. Worth noting this when looking at whether progress is as expected. A greater number of months for the same region and resolution will take longer to complete.
885 is the batch number
012039265 I don't know the significance of.
_n at the end of a task name tells you about the number of attempts the task has had. It starts at 0 so this one is on its third and final attempt. (Which also crashed.) Some models can lead to impossible climates such as a negative pressure which will crash the task. This does not mean the science behind that particular task is wasted.

hadcm3s_a000_190012_120_888_012043413_0 A Met Office Hadley Centre coupled model of the ocean and atmosphere.These tasks run on both Linux and Mac computers. I don't know what will happen yet with new Mac's using ARM processors. This task is the first from the most recent batch.

hadam4h_d004_206711_5_886_012040267_0 A high resolution Met Office Hadley Centre global atmospheric model. This runs at two resolutions on climateprediction.net which corresponds to ~90km and ~60km. These correspond to N144 and N216 tasks that you may have seen in posts on the forums. These tasks are Linux only. The higher resolution tasks use a lot more memory and disk space.
OpenIFS@home – A global atmospheric model from the European Centre for Medium Range Weather Forecasts (ECMWF). Still in testing, these tasks can take a lot of memory. Currently Linux only but the OpenIFS platform is also available for MacOS
Edit: There has now been some testing of this task type on MacOS computers.
Edit2:hadsm4 A new model type, Linux only, yet to appear on the server status page. I will post more about this project when the release of tasks is imminent.