Merge pull request #147 from HAOYUatHZ/explorer

add LN explorer section

02_getting_started.asciidoc

@@ -9,6 +9,25 @@ The Lightning Network is accessed via software applications that can speak the L
 
 Users have the highest degree of control by running their own Bitcoin node and Lightning node. However, Lightning nodes can also use a lightweight Bitcoin client (commonly referred to as Simplified Payment Verification (SPV)) to interact with the Bitcoin blockchain.
 
+=== Lightning Explorer
+
+A Lightning network explorer is an useful tool to show the statistics of nodes, channels and network capacity.
+
+The below is an inexhaustive list (in alphanumerical order):
+
+* https://1ml.com/, 1ML Lightning explorer
+* https://explorer.acinq.co/, ACINQ's Lightning explorer, with fancy visualization
+* https://lightblock.me/, Lightblock Lightning explorer
+* https://hashxp.org/lightning/node/, hashXP Lightning explorer
+
+[TIP]
+====
+Note that if using Lightning explorers, just like in existing block explorers,
+the privacy can be a concern because, if users are careless, the website may track their IP addresses and collect their behavior records (for example, the nodes users are interested in).
+
+Also what should be noted is that, as there is no global consensus of the current Lightning graph, nor the current state of any existing channel policy, users should never rely on Lightning explorers to retrieve the most updated information. That is, Lightning explorers should only be used to gather loosely statistics of Lightning Network.
+====
+
 === Lightning Wallets
 
 The term "Lightning Wallet" is somewhat ambiguous, as it can describe a broad variety of components combined with some user interface. The most common components of lightning wallet software include:

glossary.asciidoc

@@ -277,6 +277,10 @@ Neutrino::
 node::
     See Lightning Network Node
 
+network capacity::
+    Lightning network capacity is the value of bitcoin locked and circulated inside Lightning Network and is the sum of capacities of each channel.
+    It is a mesurement of the maximum value a user can transfer in Lightning Network because routing nodes will need to have sufficient balances. It also reflects the usage of Lightning Network to some extent, because the higher value is circulated inside Lightning Network the more likely that more people are using it.
+
 Noise_XK::
     The template of the Noise protocol framework to establish an authenticated and encrypted communication channel between two peers of the Lightning Network.
     X means that no public key needs to be known from the initiator of the connection.