Buying point to point train tickets online-are you guaranteed a seat ?

With their tickets SBB makes sure you get to your destination, but it doesn’t mean you have a guaranteed seat. However, most people, especially hikers, will take earlier trains and not travel in first class, so your chances of getting a first class seat are really good.
Tour groups have to reserve seats, so SBB knows there will be many people on a certain train and if possible they add wagons to that train.
If you can’t find a seat, take a later train. They are not all full of tour groups.

Thank you Aniol.
Your advice was much appreciated.

If you bought a 1st class ticket while there is no seat left, you can get a confirmation from the train attendant. With this you can go to the ticket counter and claim the money for 1st class back (cost difference 1st/2nd class).

thank you everyone for your help.!

Trains in Switzerland are mass transit. They are used by people to go about their daily business. Most of the people you will mingle with on the trains are locals. The way they work is more like a commuter railway than a long distance railway.

Standard tickets are "open", in that they are valid for a whole day. A lot of the people on the trains will be commuters which have some sort of a pass, and they will not reserve seats either. As such reservations are uncommon, even though you can have them on some trains. As such tickets also never sell out and there is no need to buy train tickets in advance. You could buy your train ticket without any issues at the train station in Luzern on the day of travel for example. Selling you a train ticket the railway commits to transporting you to your destination. They certainly will not abandon you, keep the money and leave you to your own devices. This is a civilised country :-)

If more people board a train then there are seats than not everyone will be able to sit. Just stand and keep an eye open. At the next stop some people will for sure get off. Don't forget, most of the people on the train aren't tourists.

Are you planning more train travel in Switzerland? If so look in to maybe getting the Half Fare Card, which will also get you 50% off on mountain railways and cable cars. And are you actually going to Interlaken, or are you maybe going to Grindelwald or Wengen? In Switzerland you do not need to buy tickets for each train separately. Technically you cannot buy a train ticket. You buy a transportation ticket, and you can buy it between any two places in Switzerland, irrespective of how many trains, or other means of transport are involved in getting you there from here.

Thank you Wengen K for clearing that up.I guess I thought of train seats like airline seats as opposed to subway seats.

As you are from Wengen (it seems)id like to reserve a hotel there for 3 nights but it must be on one of the main streets so my husband does not have to go up any inclined streets.Would the main flat street be Dorfstrasse?

Thank you

We actually do not have street names in Wengen. Postal delivery relies on the postman knowing where everyone lives :-)
But the street marked "Dorfstrasse" on google maps is indeed the main street in the village, and it is more or less level from the station. So staying at Sun Star, Silberhorn, Bernerhof or Victoria Lauberhorn all puts you in the centre, and a close walk from the station. But if you are willing to walk a bit further the Berghaus is wonderful.

Thank you again Wengenk for the hotel ideas.I’m going to switch 2 of my 3 nights in Interlaken to 2 nights in Wengen.Need to catch a 10am train from Interlaken last day there so don’t want to stress about connecting from wengen on a 9am train.
Thank you again for all your help.

It's as you wish, but catching a 10am train from Interlaken starting in Wengen is really easy. The train takes 40 minutes including connecting in Lauterbtunnen, and there are departures every 30 minutes, so you do not need to wake up that early!
It will be less tiresome than dragging your luggage to Interlaken the precious evening.