The Subscriber Identity Module, or SIM card, is an essential piece of equipment in your phone. Your phone will have a broadband chip which allows it to use a cellular signal to communicate information from your device to another, but without a telephone company's SIM card, your phone will not be able to access the provider's cellular network. While the SIM card gives your phone the ability to access mobile networks, it also acts as a leash to limit your options. A new generation of SIM technology, known as the eSIM, can help to give you more freedom with how you use cellular data.
Limitations of Traditional SIM Cards
Each telephone company will create unique SIM cards, which allow your phone to access their network. The downside of a unique SIM card is that it limits your ability to access other networks. The card that allows you access to one network will disallow you access to others. You might think that switching networks should be as easy as removing one company's card and inserting another, most carrier's will only sell cell-locked phones which will only accept their company's SIM card. Apple and other manufacturers will sell unlocked phones, but they cost more than a locked phone, so they are not a feasible option for most people.
How an eSIM Can Help
Phones like Apple's new iPhone has the ability to use multiple LTE bands, which means that it can operate on all of the major networks around the world. This would make the phone great for traveling except that inserting a SIM card limits access to only one carrier's network. An eSIM card would be integrated into the hardware of the phone and would be rewritable by any provider. Thus, you could receive the code to allow you to operate on virtually any network while traveling as long as your phone has the ability to work on the LTE band the provider uses.
In the final analysis, the need to have an eSIM card on your phone depends on your travel needs. For those who rarely travel out of state or out of country, being ability to operate on multiple bands is a non-issue. You simply choose the carrier who provides the best coverage in your area and then purchase a phone with their SIM card. On the other hand, if you travel a lot for business or pleasure, purchasing a phone with an eSIM, or buying an eSIM for your phone from a company like Cloude 9 could make good sense.
I'm a travelling sales representative, and I spend a lot of time on the phone. I always used to be looking for a charger and it was a total pain. I switched to a phone model with much better battery life, and I have a power bank that I travel with that allows me to recharge on the go. Often it can make a lot of difference when you switch off apps and adjust phone features such as brightness. This blog has lots of details on what you can do to improve battery life, and it also discusses which telephone models have the best battery life.